Electric motor



G. F. PACKARD ELECTRIC MOTOR March 9 1926. I 1,576,002

Filed March 13. 1925 s Sheets-Sheet '1 Granville 1? Packard.

March 9 1926.

G. F. PACKARD ELECTRIC MOTOR Filed March 155. 1923 3 Sheets-Sheet 2 43 Fig. 9. 43

o o I I i '472 o o o I IIIIH WITNESSES: INVENTOR Granville E Packard.

' I BY Fig 12 Z151? 1 NW 1 O O 0 O o G O O C) O i O L10 O muuunmn' W O O J 68 mmmmmmmummnum 63 :0 as i mummmm muumnnm O O O O O INVENTOR WITNESSES:

Pasta a. a, 1926.

UNITED STATES PATENT o-F'FicE.

- GRANVILLE PACKARD, OF WILKINSBURG, PENNSYLVANIA.

ELECTRIC moron.

/ 4 Application filed March 13, 1928. Serial No. 824,789.

.To all whom it may concern:

Be-it known that I, GRANVILLE F. PACK- ARD, acitizen of the United States, and a resident of Wilkinsburg, in the county of 6 Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Electric Motors, of which the following is a specification.

My. invention relates to electric motors,

' 1 and particularly to motors of the induction tivity.

A. further object of .my invention is to rovide a motor having improved facilities or dissipating heat from its various parts.

- I have found that the operating characteristics of a motor of the induction type may be improved by providin the rotor with perforations which rovlde definite paths for eddy currents t at may be induced-therein by the primary core structure. I have found, also, that the operating characteristics of such motors may be improved by'providin the rotors with portions the magnetic re uctance' of which is relativelylow.

A motor constructed. in accordance with my invention is provided with ample spaces for ventilatin the various parts whereby heat may be dlssipated rapidly and eflicient' ly' therefrom. Certain of the parts are constructed ,of-double plates of relatively thin material rather-than of a single plate of relatively thickmaterial in order that the rate of dissipation of heat therefrom may be materially increased. In the accompanying drawings,

Figure 1 is a perspective view of a motor constructed in accordance with my invention,-a portion-being broken'awa Fig. 2 is a front elevational new of the core structure and asecondary plate mem-.

ber;

Fig. 3'is' a side view of the rotor;

Figs. 4 and 5 are end views of rotors hav- I ing perforations of modified form; Figs. 6 and 7 are end views of rotors in which the perforations are occupied by ma-' terial of relatively low magnetic reluctance; I

Fig. 8is an end view of a primary member and a secondary member in which the polar projections are arranged at angles to the corresponding radii;

Fig. 9 is a cross-sectional view of a motor in which certain of the members are constructed of spaced plates;

Fig. 10 is a view. in transverse section of the inotor of Fig. 9, a portion of the rotor being broken away;

Fig. 11 is a view inlongitudinal section of a motor provided with a plurality of windings and magnetic circuits;

Fig. 12 is an end view of the primary member and a secondary plate member of the-motor of Fig. 11;

' Fig. 13 is a view similar to Fig. 11 of a modification;

Fig. 14 is an end View; 'of the core structure of the motor of Fig. 13.

The motor shown in Figs. 1, 2 and 3 comprises a stationary core structure 1 of laminations extending longitudinally of the motor axis. The laminations are divided into two spaced groups 2 and 3, an upper and a lower group, as viewed in Fi 1 and 2. 'Each group'is suitably recesse at each end across its central ortion whereby the two pairs of polar pro ections 5 and 6 thus constituted may be surrounded by a secondary plate member 7 Each of the secondary plate members 7 is provided with slits 8 and 9 adjacent to dia onally opposite olar rojections 5, while the polar project pns 6 a i'e surrounded by a continuous band of metal to constitute the equivalent of a shading coil. The secondary plates are provided with suitable holes 11 for bolts 12 and 13 for retaining them inassembled position, the bolt 13 con-. stitjuting aconvenient handle for the motor. A central hole 14 is also provided to constitute 'a bearing forthe shaft 15 of a rotor 16.

The rotor 16 comprisesa pair of'dislm 17.

that are mounted on the respective ends of the shaft 15 and adjacent to the corresponding polar projections 5 and 6'. A hub 18 -on each end of the shaft has a groove 19,

structure" insures that a greater percentage e of flux from the poles passes through t plane of the disk and correspondingly increases the efficiency of the motor.

The operation of the motor occurs when the coil 21 is energized. The poles 5 and 6 would ordinarily be of the same polarity simultaneously but the latter are surrounded by the plates 7 which constitute secondary windings or shading coils to cause the poles 6 to be out of phase with the poles 5 as will be understood. Rotation of the rotor is accordingly caused by the reactions between the poles 6 and the fields established byeddy currents in the disks 17 induced by flux from the poles 5.

The theory of the operation of a motor of the same general character as that of my present invention is described in my Patent Y 1,534,282.

The perforations 20 in the rotor disks have a two-fold purpose. In addition to insuring better ventilation and dissipation of heat from the rotor, the paths of eddy currents induced by the poles 5. and 6 are limited to the conducting material surrounding"the perforations- Iha-ve found that the provision of a rotor thus constructed materially improves the torque and other operating characteristics of the motor.

of the members of the pairs of While the reasons for the improvement above noted are not definitely known, it is probable that the perforations prevent shiftmg angularly of the currents induced in the rotor disks 17 and tend to cause the latter to rotate in synchronism with what are, in

effect, rotating fields established by the phase displacement of the magnetization In the rotor disk,24 shown m Fig. 4, the perforations'25 are triangular in form, the structure resembling a wheel with spokes radiating from a central hub portion.

In the modification shown m Fig. 5, the perforations 26 are circular in form, the centers of the .circles and the centers of the polar projections being substantially equidistant-from the motor axis.

In the rotor- 27 of Fig. 6, the perforations 28- areat an angle to the corresponding radii. The perforations are occupied by maternal of or reluctance, such, 'for example, as iron indicated at 25 in order to increase the roportion of useful flux through the disii and thereby corresponding- .ly increase the strengths of the magnetic fields induced therein. The angularity of the perforations is such that ad acent ones overlap each other whereby some portion of at least one of them is in alinement with each of the poles. This arrangement insures that a substantially uniform'flux traverses the disk irrespective of its angular position.

The disk 31 shown in Fig. 7 has radiallyextending perforations 32 that are similar in shape to those of Fig. 6. The perforations 32 are occupied by material of low reluctance. The number of perforations is relatively large whereby the flux traversing stantially uniform in its variforations in the various forms of, rotors shown and described herein are even numbers and that, in most instances, the numher is a'multiple of the number of pairs of poles shown in the motor of Fig. 1. However, I have found that the motor will op eratc satisfactorily when an odd number of perforations is employed or when the number is not a multiple of the numbers of poles of the primary member.

In Fig. 8, I have illustrated a primary core structure 34 and a secondary plate 35 wherein the pairs of polar projections 36 and 37 and the corresponding openings in the plate are inclined to the radil passing therethrough. This structure is, :in effect, a reversal of parts of a motor of the type of Fig. 1 havlng a rotor with inclined perforations such as that of Fig. 6.

The motor 40 shown in Figs. 9 and 10 differs from that of Fig. 1 in a number of features. The pairs of polar projections 41 and 42, which are disposed circumferentially about the motor axis, extend radially therefrom. The secondary plates 43 consist of nated structure 47 is of rectangular shape and constitutes a casing for the motor. The casing provides return paths of low reluctance for flux traversing the disks of the rotors. A single energizing coil '48 surrounds the groups of lamination The motor of Figs. 9 and 10 operates with high efiiciency because of the very low reluctanceof the magnetic paths comprising the laminations 46. The eifect of the perforations is substantially unchanged by the presence of the laminations 46 since eddy currents do not traverse them circumferentially of the disk 44. The spaced arrangement of the parts insures ample ventilatlon to prevent excessive heating.

Reference may now be had to the modification illustrated in Figs. 11 and 12. The structure 50 consists of laminations 51 of approximately H-shape that constitute the primary core member 52 and the top and the bottom of the casing for the motor and of laminations 53 that constitute the end portions of the casing. Each end of the core member 52 is provided with a secondary plate member 54 that is similar to those of Fig. 1 exceptin shape.

A coil 55 surrounds each end of the core member 52. A rotor comprises a disk 56v adjacent to'each end of the core member 52,

- the disks being of the perforated type of cipal parts of themotors any of the forms hereinbefore described.

The principal characteristics of the motor of Figs. 11 and 12 are that parallel magnetic circuits of relatively short length are provided whereby the. reluctances are relatively low and that, in efi'ect, two motors are provided in a single unitary structure with a single rotatable member.

The motor of Figs. 13 and 14 is similar to that of the motor just described exce t the secondary plate members 58 are dlsposed around polar projections 59 and 60 thatare provided on the laminations 61 constituting the end portions of the casing. The ends'of the core member 62 are notched at 63 to prevent leakage of flux between other than thepoles and adjacent parts, in alinement therewith.

v The motors of. Figs. 11 and 12 and Figs. 13 and 14 operate on the sameprinciples as the, motor of Fig. 1.

While I have shown the laminations of certain of the several core members as extending transversely to the lines joining the members of the several airs of polar prole 1n certain cases to arrange the laminationsparallel to such lines as in the poles 41 and 42 of Fig. 10.

The transverse arrangement appears to have :the desirable characteristic of preventing local circuits of ma' etic flux when the coacting poles are dls laced in phase and, therefore, are of difi rent polarlty' at certain portions of the cycles of the singlephase source of energy It will be understood that the several princonstructed in accordance with my invention are susceptible of many changes in arrangement of parts,

of .paths for magnetic and electrical circuits and in materials mplo ed and that my invention is not limite to thev structures at least one shown and described herein cated by the appended claims.

'I claim as my invention:

1. An electric motor comprising a primary member having a plurality of pairs of polar projections and a rotor comprising a disc having a plurality of separate mem: bers, of magnetic material extending therethrough, the number of said last-named members being a multiple of the number of pairs of polar projections.

2. An electric motor comprising a primary member having a plurality of polar projections and a disc inductively related thereto, said disc having a plurality of perforations extending at an angle relativelyto the corresponding polar projections. 3. An electric motor comprising a primary member having a plurality of polar projections and a disc inductively related thereto, said disc having a plurality of magnetizable members therein, said members being inclined relatively to the corresponding polar projections.

11 electric motor comprising a primary member having a plurality of polar projections and a disc inductively related thereto, said disc having a plurality of perforations extending at such angle relatively to the corresponding polar projections that of said perforations is always in a-linement tions.

5. An electric motor comprising a primary member having a plurality of polar projections and a disc inductively related thereto, said disc having a plurality of magnetizable members therein, said members being so inclined relatively to the corresponding polar projections that at least one of said magnetizable members is always in alinement tions.

6. An electric motor comprising a primary member having a core structure with poles certain of which are provided with shading coils, a magnetizing coil, and a pair of rotatable discs having a common shaft and coacting with said poles, said discs being provided with perforations having magnetic material disposed therein to aline with said poles, corresponding perforations and pole faces having different angles relatively to' the same radii of said discs.

7. An electric motor comprising an exter-.

except as indiwith each of said polar projecwith each of said polar projecto said polar projections comprising a plu-' rality of spaced perforated disks having ma netizable members in the perforations an extending between said disks.

11. A motive device having a primary member provided with longitudinally-extending polar projections and a secondary -member comprising a plate member having openings through which said projections extend to provide shading coils for certain of said projections. v

12. An electric motor comprising a sta tionary external field structure, an internal core structure supported thereby and having a plurality of longitudinally-extending polar projections at each end thereof, a magnetizing coil surrounding each end of said core structure, and a rotor inductively related to each group of polar projections.

13. A motive device having a primary member provided with a plurality of polar projections, a plate member of conducting material having openings through which certain of said polar projections extend, and a rotatable secondary'jjmember adjacent to said plate member.

14. A motive device comprising a primary member having a magnetizable portion pro-' vided with a plurality of polar projections and having, also, a plate member of conducting material through which said projections extend to provide shading coils for certain of said projections, the" plate member being provided with slits adjacent to the remaining projections to maintain an open circuit therearound, and a rotor coacting with said primary member.

In testimony whereof, I have hereunto subscribed my name this 1st day of March 1923.

' GRANVILLE r. PACKARD. 

